This project is designed to determine whether immunization of mice with a recombinant DNA-derived onc gene product can lead to protection against a subsequent challenge with tumor cells expressing this onc gene product. Immunization of BALB/c mice will be performed with a highly purified recombinant DNA-derived Haras onc gene product, p21. Mice will subsequently be challenged with 100,000 Harvey sarcoma virus of Kirsten sarcoma virus transformed BALB/3T3 cells in order to determine if protective immunization has been achieved. Cellular immune responses to the onc gene product will also be investigated. Subsequent studies will utilize other recombinant DNA derived onc gene products (e.g. mos) to determine the immunization potential of these proteins. These experiments will provide an important evaluation of the potential usefulness of onc gene products as immune stimuli of host defenses against cancer.